Light emitting diode having side reflection layer

ABSTRACT

A light emitting diode including a side reflection layer. The light emitting diode includes: a semiconductor stack and a light exit surface having a roughened surface through which light generated from an active layer is emitted; side surfaces defining the light exit surface; and a side reflection layer covering at least part of the side surfaces. The light exit surface is disposed over a first conductivity type semiconductor layer opposite to the ohmic reflection layer, all layers from the active layer to the light exit surface are formed of gallium nitride-based semiconductors, and a distance from the active layer to the light exit surface is 50 μm or more.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.16/789,215, filed on Feb. 12, 2020, which is a Continuation of U.S.patent application Ser. No. 15/811,900, filed on Nov. 14, 2017, whichissued as U.S. Pat. No. 10,749,078, and claims priority from and thebenefit of U.S. Provisional Application Nos. 62/422,015, filed on Nov.14, 2016, and 62/461,405, filed on Feb. 21, 2017, all of which areincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND Field

Exemplary embodiments of the present disclosure relate to a lightemitting diode and, more particularly, a light emitting diode includinga side reflection layer to adjust a viewing angle.

Discussion of the Background

Recently, with good thermal stability and a direct transition typeenergy band structure, Group III-based nitrides such as gallium nitride(GaN), aluminum nitride (AlN), and the like have been spotlighted asmaterials for light sources in the visible range and the ultravioletrange. Particularly, blue and green light emitting diodes using indiumgallium nitride (InGaN) are used in various application fields includinglarge natural color flat displays, signal lamps, interior lighting, highdensity light sources, camera flash, high resolution output systems,optical communication, and the like. Furthermore, the light emittingdiodes exhibit good straight propagation of light and thus, are broadlyused in a headlamp for automobiles.

Some applications of light emitting diodes often require the lightemitting diodes to have a narrow viewing angle. Particularly, lightemitting diodes having a narrower viewing angle are more advantageouslyapplicable to automobile headlamps or camera flashes. In addition, whena backlight light source module configured to spread light through alens is used as in LED TVs, discharge of light emitted from a sidesurface of a light emitting diode through the lens is difficult, therebycausing increase in light loss. Therefore, there is a need for a lightemitting diode that can reflect light reaching a side surface thereof toallow the light to be emitted within the range of narrow viewing angles.

SUMMARY

Exemplary embodiments of the present disclosure provide a light emittingdiode having a narrow viewing angle.

Exemplary embodiments of the present disclosure provide a light emittingdiode that has a narrow light viewing angle by reducing the amount oflight emitted through a side surface thereof.

Exemplary embodiments of the present disclosure provide a light emittingdiode that allows easy control of viewing angle.

Exemplary embodiments of the present disclosure provide a light emittingdiode that can realize a narrow viewing angle while reducing deviationin electrical characteristics between light emitting diodes.

In accordance with one aspect of the present disclosure, a lightemitting diode includes: a semiconductor stack including a firstconductivity type semiconductor layer, a second conductivity typesemiconductor layer, and an active layer interposed between the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer; an ohmic reflection layer electrically connected tothe second conductivity type semiconductor layer; a first bump pad and asecond bump pad disposed under the ohmic reflection layer andelectrically connected to the first conductivity type semiconductorlayer and the second conductivity type semiconductor layer,respectively; a light exit surface having a roughened surface throughwhich light generated from the active layer is emitted; side surfacesdefining the light exit surface; and a side reflection layer covering atleast part of the side surfaces. The light exit surface is disposed overthe first conductivity type semiconductor layer opposite to the ohmicreflection layer, all layers from the active layer to the light exitsurface are formed of gallium nitride-based semiconductors, and adistance from the active layer to the light exit surface is 50 μm ormore.

In accordance with another aspect of the present disclosure, a lightemitting diode includes: a substrate having a side surface; asemiconductor stack disposed under the substrate and including a firstconductivity type semiconductor layer, a second conductivity typesemiconductor layer, and an active layer interposed between the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer; an ohmic reflection layer electrically connected tothe second conductivity type semiconductor layer; a first bump pad and asecond bump pad disposed under the ohmic reflection layer andelectrically connected to the first conductivity type semiconductorlayer and the second conductivity type semiconductor layer,respectively; and a side reflection layer covering the side surface ofthe substrate.

In accordance with further aspect of the present disclosure, a lightemitting diode includes: a substrate having a side surface; a firstconductivity type semiconductor layer disposed under the substrate; amesa disposed under the first conductivity type semiconductor layer andincluding an active layer and a second conductivity type semiconductorlayer; an ohmic reflection layer covering the second conductivity typesemiconductor layer; a lower insulation layer covering the ohmicreflection layer and including a first opening exposing the firstconductivity type semiconductor layer and a second opening exposing theohmic reflection layer; a first pad metal layer disposed on the lowerinsulation layer and electrically connected to the first conductivitytype semiconductor layer through the first opening; a first bump padelectrically connected to the first pad metal layer; a second bump padelectrically connected to the ohmic reflection layer; and a sidereflection layer covering the side surface of the substrate. The sidereflection layer is spaced apart from the first pad metal layer in alateral direction so as not to overlap the first pad metal layer.

Exemplary embodiments of the present disclosure provide light emittingdiodes that employ a side reflection layer and have a distance of 50 μmfrom an active layer to a light exit surface, thereby providing aviewing angle of 110 degrees or less. Furthermore, exemplary embodimentsof the present disclosure provide light emitting diodes that exhibitgood electrical reliability and low deviation in electricalcharacteristics therebetween by preventing short circuit whilemaintaining the distance between the side reflection layer and a metallayer.

Exemplary embodiments of the present disclosure provide light emittingdiodes that employ a side reflection layer to have a narrow viewingangle by reducing the amount of light emitted through side surfacesthereof and can permit easy adjustment of the viewing angle throughadjustment of a location of the side reflection layer. Furthermore, theside reflection layer is formed to be spaced apart from a first padmetal layer in the lateral direction to prevent electric connectionbetween the side reflection layer and the pad metal layer, therebysecuring good electrical stability.

Other advantages and effects of the exemplary embodiments of the presentdisclosure will become apparent from the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosed technology, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the disclosed technology, and together with thedescription serve to describe the principles of the disclosedtechnology.

FIG. 1 is a schematic plan view of a light emitting diode according toone exemplary embodiment of the present disclosure.

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1.

FIG. 3 is a schematic cross-sectional view of a light emitting diodeaccording to another exemplary embodiment of the present disclosure.

FIG. 4 is a schematic cross-sectional view of a light emitting diodeaccording to a further exemplary embodiment of the present disclosure.

FIG. 5 is a schematic cross-sectional view of a light emitting diodeaccording to yet another exemplary embodiment of the present disclosure.

FIG. 6 is a schematic cross-sectional view of a light emitting diodeaccording to yet another exemplary embodiment of the present disclosure.

FIG. 7 is a schematic cross-sectional view of a light emitting diodeaccording to yet another exemplary embodiment of the present disclosure.

FIG. 8 is a schematic cross-sectional view of a light emitting diodeaccording to yet another exemplary embodiment of the present disclosure.

FIG. 9A, FIG. 9B, FIG. 10A, FIG. 10B, FIG. 11A, FIG. 11B, FIG. 12A, FIG.12B, FIG. 13A, FIG. 13B, FIG. 14A, FIG. 14B, FIG. 15A, FIG. 15B, FIG.16A, FIG. 16B, FIG. 17A, FIG. 17B, FIG. 17C and FIG. 17D are schematicplan views and cross-sectional views illustrating a method ofmanufacturing a light emitting diode according to one exemplaryembodiment of the present disclosure.

FIG. 18A, FIG. 18B, FIG. 18C and FIG. 18D are schematic cross-sectionalviews illustrating a method of manufacturing a light emitting diodeaccording to a further exemplary embodiment of the present disclosure.

FIG. 19 is a schematic cross-sectional view illustrating a method ofmanufacturing a light emitting diode according to yet another exemplaryembodiment of the present disclosure.

FIG. 20A, FIG. 20B, FIG. 20C and FIG. 20D are schematic cross-sectionalviews illustrating a method of manufacturing a light emitting diodeaccording to yet another exemplary embodiment of the present disclosure.

FIG. 21 is a schematic sectional view of a light emitting moduleaccording to one exemplary embodiment of the present disclosure.

FIG. 22 is a schematic sectional view of a light source module accordingto one exemplary embodiment of the present disclosure.

FIG. 23 is a schematic perspective view of an automobile includingheadlamps to which light emitting diodes according to exemplaryembodiments of the present disclosure are applied.

FIG. 24 is a schematic perspective view of a mobile device including acamera flash to which light emitting diodes according to exemplaryembodiments of the present disclosure are applied.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Thefollowing embodiments are provided by way of example so as to fullyconvey the spirit of the present disclosure to those skilled in the artto which the present disclosure pertains. Accordingly, the presentdisclosure is not limited to the embodiments disclosed herein and canalso be implemented in different forms. In the drawings, widths,lengths, thicknesses, and the like of elements can be exaggerated forclarity and descriptive purposes. When an element is referred to asbeing “disposed above” or “disposed on” another element, it can bedirectly “disposed above” or “disposed on” the other element, orintervening elements can be present. Throughout the specification, likereference numerals denote like elements having the same or similarfunctions.

In accordance with one exemplary embodiment of the present disclosure, alight emitting diode includes: a semiconductor stack including a firstconductivity type semiconductor layer, a second conductivity typesemiconductor layer, and an active layer interposed between the firstconductivity type semiconductor layer and the second conductivity typesemiconductor layer; an ohmic reflection layer electrically connected tothe second conductivity type semiconductor layer; a first bump pad and asecond bump pad disposed under the ohmic reflection layer andelectrically connected to the first conductivity type semiconductorlayer and s the second conductivity type semiconductor layer,respectively; a light exit surface having a roughened surface throughwhich light generated from the active layer is emitted; side surfacesdefining the light exit surface; and a side reflection layer covering atleast part of the side surfaces. The light exit surface is disposed overthe first conductivity type semiconductor layer opposite to the ohmicreflection layer, all layers from the active layer to the light exitsurface are formed of gallium nitride-based semiconductors, and adistance from the active layer to the light exit surface is 50 μm ormore.

The side surfaces may include a perpendicular side surface perpendicularto an upper surface of the first conductivity type semiconductor layerand an inclined side surface inclined with respect to the perpendicularside surface, and the perpendicular side surface may be closer to thelight exit surface than the inclined side surface.

The inclined side surface may have an inclination angle of about 10degrees or more with respect to the perpendicular side surface.

The side reflection layer may cover the perpendicular side surface andthe inclined side surface.

The light emitting diode may further include a mesa disposed on thefirst conductivity type semiconductor layer, wherein the mesa includesthe active layer and the second conductivity type semiconductor layer.In addition, the mesa may be spaced apart from the side surfaces and theside reflection layer may be disposed only on the side surfaces.

The light emitting diode may further include: a lower insulation layercovering the ohmic reflection layer, the lower insulation layer having afirst opening exposing the first conductivity type semiconductor layerand a second opening exposing the ohmic reflection layer; a first padmetal layer disposed on the lower insulation layer and electricallyconnected to the first conductivity type semiconductor layer through thefirst opening; a second pad metal layer disposed on the lower insulationlayer and electrically connected to the ohmic reflection layer throughthe second opening; and an upper insulation layer covering the first padmetal layer and the second pad metal layer, the upper insulation layerhaving a first opening exposing the first pad metal layer and a secondopening exposing the second pad metal layer, wherein the first andsecond bump pads are disposed on the upper insulation layer andelectrically connected to the first pad metal layer and the second padmetal layer through the first opening and the second opening of theupper insulation layer, respectively.

The mesa may include a through-hole formed through the secondconductivity type semiconductor layer and the active layer to expose thefirst conductivity type semiconductor layer, and the first pad metallayer may be electrically connected to the first conductivity typesemiconductor layer exposed through the through-hole.

The mesa may further include an indented portion formed on side surfacesthereof to expose the first conductivity type semiconductor layer, andthe first pad metal layer may be electrically connected to the firstconductivity type semiconductor layer exposed through the indentedportion.

The mesa may have corners each having a cut shape and the first padmetal layer may be electrically connected to the first conductivity typesemiconductor layer near the corners of the mesa.

In some exemplary embodiments, the light emitting diode may furtherinclude an ohmic oxide layer disposed on the second conductivity typesemiconductor layer around the ohmic reflection layer.

In some exemplary embodiments, the light emitting diode may furtherinclude a gallium nitride-based substrate disposed on the firstconductivity type semiconductor layer, wherein the light exit surface isformed on the gallium nitride-based substrate and the side reflectionlayer covers a side surface of the substrate and a side surface of thefirst conductivity type semiconductor layer.

The light emitting diode may have a light viewing angle of 110 degreesor less.

In accordance with another exemplary embodiment of the presentdisclosure, a light emitting diode includes: a substrate including alight exit surface having a roughened surface and side surfaces; a firstconductivity type semiconductor layer disposed on the substrate; a mesadisposed on the first conductivity type semiconductor layer andincluding an active layer and a second conductivity type semiconductorlayer; an ohmic reflection layer covering the second conductivity typesemiconductor layer; a lower insulation layer covering the ohmicreflection layer, the lower insulation layer having a first openingexposing the first conductivity type semiconductor layer and a secondopening exposing the ohmic reflection layer; a first pad metal layerdisposed on the lower insulation layer and electrically connected to thefirst conductivity type semiconductor layer through the first opening; afirst bump pad electrically connected to the first pad metal layer; asecond bump pad electrically connected to the ohmic reflection layer;and a side reflection layer covering the side surfaces of the substrateand a side surface of the second conductivity type semiconductor layer.The side reflection layer is spaced apart from the first pad metal layerin a lateral direction so as not to overlap the first pad metal layer.

The side reflection layer may be disposed only on the side surfaces ofthe substrate and a side surface of the first conductivity typesemiconductor layer. Specifically, the side reflection layer is spacedapart from the mesa and from an exposed surface of the firstconductivity type semiconductor layer around the mesa.

The light emitting diode may further include: a second pad metal layerdisposed on the lower insulation layer and electrically connected to theohmic reflection layer through the second opening; and an upperinsulation layer covering the first pad metal layer and the second padmetal layer, the upper insulation layer having a first opening exposingthe first pad metal layer and a second opening exposing the second padmetal layer, wherein the second bump pad may be connected to the secondpad metal layer through the second opening of the upper insulationlayer.

In some exemplary embodiments, the side surface of the substrate mayinclude a perpendicular side surface perpendicular to the light exitsurface and an inclined side surface inclined with respect to theperpendicular side surface, and the side reflection layer may cover theperpendicular side surface and the inclined side surface.

The side reflection layer on the perpendicular side surface and inclinedside surface may have a substantially uniform thickness.

In some exemplary embodiments, the light emitting diode may furtherinclude an insulation layer interposed between the inclined side surfaceand the side reflection layer.

One end of the side reflection layer may be flushed with or may bespaced apart from a surface of the first conductivity type semiconductorlayer around the mesa.

In some exemplary embodiments, the mesa may include a through-holeformed through the second conductivity type semiconductor layer and theactive layer to expose the first conductivity type semiconductor layer;and an indented portion formed on side surfaces of the mesa and exposingthe first conductivity type semiconductor layer, wherein the first padmetal layer is electrically connected to the first conductivity typesemiconductor layer exposed to the through-hole and the indentedportion.

The first pad metal layer may be electrically connected to the firstconductivity type semiconductor layer near corners of the mesa. Withthis structure, the light emitting diode allow uniform spreading ofelectric current therein.

The side reflection layer may include a metal reflection layer or adistributed Bragg reflector.

In accordance with another exemplary embodiment of the presentdisclosure, a light emitting diode includes: a substrate having a sidesurface; a semiconductor stack disposed under the substrate andincluding a first conductivity type semiconductor layer, a secondconductivity type semiconductor layer, and an active layer interposedbetween the first conductivity type semiconductor layer and the secondconductivity type semiconductor layer; an ohmic reflection layerelectrically connected to the second conductivity type semiconductorlayer; a first bump pad and a second bump pad disposed under the ohmicreflection layer and electrically connected to the first conductivitytype semiconductor layer and the second conductivity type semiconductorlayer, respectively; and a side reflection layer covering the sidesurface of the substrate.

The side reflection layer serves to reduce the light viewing angle ofthe light emitting diode by reflecting light reaching the side surfaceof the substrate.

In one exemplary embodiment, the side surface of the substrate includesa perpendicular side surface perpendicular to an upper surface of thefirst conductivity type semiconductor layer and an inclined side surfaceinclined with respect to the perpendicular side surface. The sidereflection layer may cover at least the perpendicular side surface.

The inclined side surface may have an inclination angle of about 10degrees or more with respect to the perpendicular side surface.

The perpendicular side surface may be closer to an upper surface of thesubstrate than the inclined side surface. The side reflection layer mayalso cover the inclined side surface. The light emitting diode mayfurther include an insulation layer interposed between the inclined sidesurface and the side reflection layer.

In another exemplary embodiment, the inclined side surface may be closerto an upper surface of the substrate than the perpendicular sidesurface.

The side reflection layer may cover the inclined side surface. However,it should be understood that other implementations are also possible.Alternatively, the side reflection layer may cover the perpendicularside surface excluding the inclined side surface. The viewing angle ofthe light emitting diode can be adjusted by changing the location of theside reflection layer.

The side surface of the substrate may be perpendicular to an uppersurface of the first conductivity type semiconductor layer.

In one exemplary embodiment, the side reflection layer may cover theentirety of the side surface of the substrate. In another exemplaryembodiment, the side reflection layer may cover the side surface of thesubstrate in a plurality of band shapes spaced apart from each other.

Accordingly, the side surface of the substrate may be partially exposedthrough the side reflection layer and some fraction of light may beemitted through the exposed regions of the side surface of thesubstrate.

In some exemplary embodiments, the substrate may have a roughenedsurface formed on the upper surface thereof such that light generatedfrom the active layer can be emitted through the roughened surface. Theroughened surface enhances efficiency in extraction of light.

The light emitting diode may include a mesa disposed on the firstconductivity type semiconductor layer. The mesa includes the activelayer and the second conductivity type semiconductor layer and is spacedapart from the side surfaces. In addition, the side reflection layer maybe spaced apart from the mesa in a lateral direction.

The light emitting diode may further include: a lower insulation layercovering the ohmic reflection layer, the lower insulation layerincluding a first opening exposing the first conductivity typesemiconductor layer and a second opening exposing the ohmic reflectionlayer; a first pad metal layer disposed on the lower insulation layerand electrically connected to the first conductivity type semiconductorlayer through the first opening; a second pad metal layer disposed onthe lower insulation layer and electrically connected to the ohmicreflection layer through the second opening; and an upper insulationlayer covering the first pad metal layer and the second pad metal layer,the upper insulation layer including a first opening exposing the firstpad metal layer and a second opening exposing the second pad metallayer. The first and second bump pads are disposed on the upperinsulation layer and electrically connected to the first pad metal layerand the second pad metal layer through the first opening and the secondopening of the upper insulation layer, respectively.

The mesa may include a through-hole formed through the secondconductivity type semiconductor layer and the active layer to expose thefirst conductivity type semiconductor layer, and the first pad metallayer may be electrically connected to the first conductivity typesemiconductor layer exposed through the through-hole.

The mesa may further include an indented portion formed on side surfacesthereof to expose the first conductivity type semiconductor layer, andthe first pad metal layer may be electrically connected to the firstconductivity type semiconductor layer exposed through the indentedportion.

The mesa may have corners each having a cut shape and the first padmetal layer may be electrically connected to the first conductivity typesemiconductor layer near the corners of the mesa.

The side reflection layer may include a metal reflection layer. Inaddition, the substrate may be a sapphire substrate or a galliumnitride-based substrate.

In accordance with further exemplary embodiment of the presentdisclosure, a light emitting diode includes: a substrate having a sidesurface; a first conductivity type semiconductor layer disposed underthe substrate; a mesa disposed under the first conductivity typesemiconductor layer and including an active layer and a secondconductivity type semiconductor layer; an ohmic reflection layercovering the second conductivity type semiconductor layer; a lowerinsulation layer covering the ohmic reflection layer, the lowerinsulation layer including a first opening exposing the firstconductivity type semiconductor layer and a second opening exposing theohmic reflection layer; a first pad metal layer disposed on the lowerinsulation layer and electrically connected to the first conductivitytype semiconductor layer through the first opening; a first bump padelectrically connected to the first pad metal layer; a second bump padelectrically connected to the ohmic reflection layer; and a sidereflection layer covering the side surface of the substrate. The sidereflection layer is spaced apart from the first pad metal layer in alateral direction so as not to overlap the first pad metal layer.

Since the side reflection layer is spaced apart from the first pad metallayer in the lateral direction, the light emitting diode can preventunnecessary electrical connection therebetween, thereby improvingelectrical stability of the light emitting diode.

The light emitting diode may further include: a second pad metal layerdisposed on the lower insulation layer and electrically connected to theohmic reflection layer through the second opening; and an upperinsulation layer covering the first pad metal layer and the second padmetal layer, the upper insulation layer including a first openingexposing the first pad metal layer and a second opening exposing thesecond pad metal layer. The second bump pad is connected to the secondpad metal layer through the second opening of the upper insulationlayer.

The side surface of the substrate may include a perpendicular sidesurface perpendicular to a light exit surface and an inclined sidesurface inclined with respect to the perpendicular side surface, and theside reflection layer may cover at least the perpendicular side surface.

The side reflection layer may include a metal reflection layer.

Exemplary embodiments of the present disclosure will be described inmore detail with reference to the accompanying drawings.

FIG. 1 is a schematic plan view of a light emitting diode 100 accordingto one exemplary embodiment of the present disclosure and FIG. 2 is across-sectional view taken along line A-A of FIG. 1.

Referring to FIG. 1 and FIG. 2, the light emitting diode 100 includes asubstrate 21, a first conductivity type semiconductor layer 23, anactive layer 25, a second conductivity type semiconductor layer 27, anohmic reflection layer 31, a lower insulation layer 33, a first padmetal layer 35 a, a second pad metal layer 35 b, an upper insulationlayer 37, a first bump pad 39 a, a second bump pad 39 b, and a sidereflection layer 41. The first conductivity type semiconductor layer 23,the active layer 25 and the second conductivity type semiconductor layer27 constitute a semiconductor stack 30. The light emitting diode mayfurther include a transparent ohmic layer or an ohmic oxide layer 29.

The substrate 21 is a substrate that allows growth of galliumnitride-based semiconductor layers thereon, and may be, for example, asapphire substrate or a gallium nitride-based substrate. The sapphiresubstrate may be used in growth of gallium nitride-based semiconductorlayers at relatively low cost. The gallium nitride-based substrate hasan index of refraction the same as or similar to that of the firstconductivity type semiconductor layer 23. Thus, light emitted from theactive layer 25 can enter the substrate 21 without suffering fromsignificant variation in refraction, thereby improving luminousefficacy. The substrate 21 has a roughened surface R formed on an uppersurface thereof such that light can be emitted through the roughenedsurface of the substrate. Accordingly, the light emitting diode can havean improved efficiency in the extraction of light.

A light viewing angle of the light emitting diode is decreased withincreasing distance from the active layer 23 to the upper surface of thesubstrate 21. This distance is 50 μm or more, for example, 500 μm orless, specifically 300 μm or less, without being limited thereto. Thesubstrate 21 may have various sizes, without being limited to aparticular size.

Although the substrate 21 is a growth substrate in this exemplaryembodiment, it should be understood that other implementations are alsopossible. Alternatively, the substrate may be a relatively thick galliumnitride-based semiconductor layer grown on a separate growth substrate.The separate growth substrate can be removed. Alternatively, acontinuous layer of the first conductivity type semiconductor layer 23may be used instead of the substrate. The separate growth substrate canbe removed.

The substrate 21 may include a perpendicular side surface perpendicularto a lower surface of the substrate 21 and an inclined side surface withrespect to the perpendicular side surface. An angle defined between theperpendicular side surface and the inclined side surface may be about 10degrees or more. An inclination angle of the perpendicular side surfacemay be determined by scribing. Laser scribing provides a steeperinclination angle than blade scribing. A boundary between theperpendicular side surface and the inclined side surface is indicated bya dotted line. The perpendicular side surface and the inclined sidesurface may be formed on all four side surfaces of the substrate 21.

The first conductivity type semiconductor layer 23 may be disposed onthe substrate 21. Particularly, the first conductivity typesemiconductor layer 23 is disposed adjacent to the inclined side surfaceof the substrate 21. The first conductivity type semiconductor layer 23may be a layer grown on the substrate 21 or a gallium nitride-basedsemiconductor layer. The first conductivity type semiconductor layer 23may be a gallium nitride-based semiconductor layer doped with dopants,for example, Si. Here, although the first conductivity typesemiconductor layer 23 is illustrated as being clearly differentiatedfrom the substrate 21, the boundary between the first conductivity typesemiconductor layer 23 and the substrate 21may not be so clearlydefined. That is, when the first conductivity type semiconductor layer23 and the substrate 21 are formed of the same material, it can bedifficult to clearly distinguish the boundary therebetween. As shown inthe drawings, part of the inclined side surface may include the firstconductivity type semiconductor layer 23.

A mesa M is disposed on the first conductivity type semiconductor layer23. The mesa M may be disposed only inside a region surrounded by thefirst conductivity type semiconductor layer 23 such that regions nearedges of the first conductivity type semiconductor layer can be exposedto the outside instead of being covered by the mesa M.

The mesa M may include the second conductivity type semiconductor layer27 and the active layer 25. In addition, the mesa M may include aportion of the first conductivity type semiconductor layer 23 in athickness direction thereof. The active layer 25 is interposed betweenthe first conductivity type semiconductor layer 23 and the secondconductivity type semiconductor layer 27. The active layer 25 may have asingle quantum well structure or a multi-quantum well structure. Thecomposition and thickness of well layers in the active layer 25determine wavelengths of light generated from the active layer.Particularly, it is possible to provide an active layer generating UVlight, blue light, or green light through adjustment of the compositionof the well layers.

The second conductivity type semiconductor layer 27 may be a galliumnitride-based semiconductor layer doped with p-type dopants, forexample, Mg. Each of the first conductivity type semiconductor layer 23and the second conductivity type semiconductor layer 27 may be composedof a single layer or multiple layers and may include super latticelayers, without being limited thereto. The first conductivity typesemiconductor layer 23, the active layer 25, and the second conductivitytype semiconductor layer 27 may be grown on the substrate within achamber by any well-known method, such as metal organic chemical vapordeposition (MOCVD) or molecular beam epitaxy (MBE).

The mesa M may have an inclined side surface so as to have a graduallynarrowing area with increasing distance from the first conductivity typesemiconductor layer 23. The mesa M may have a gentler inclination thanthe inclined side surface of the substrate 21. However, it should beunderstood that other implementations are also possible. Alternatively,the inclined side surface of the substrate 21 may have a gentlerinclination than the side surface of the mesa M.

The mesa M includes a through-hole 30 a formed through the secondconductivity type semiconductor layer 27 and the active layer 25 toexpose the first conductivity type semiconductor layer 23. Thethrough-hole 30 a is surrounded by the second conductivity typesemiconductor layer 27 and the active layer 25. The mesa M may have asubstantially rectangular shape with cut corners. The mesa M may furtherinclude an indented portion 30 b exposing the first conductivity typesemiconductor layer 23. The indented portion 30 b is partiallysurrounded by the second conductivity type semiconductor layer 27 andthe active layer 25. The indented portion 30 b may be formed on all fourside surfaces of the mesa M, without being limited thereto.Alternatively, the indented portion may be restrictively formed on oneto three side surfaces of the mesa. Sidewalls of the through-hole 30 aand the indented portion 30 b may be inclined similar to that of theside surface of the mesa M. The sidewalls of the through-hole and theindented portion may have a gentler inclination than the inclined sidesurface of the substrate 21.

The ohmic reflection layer 31 is disposed on the mesa M to contact thesecond conductivity type semiconductor layer 27. The ohmic reflectionlayer 31 may be disposed over the entire region of an upper surface ofthe mesa M. For example, the ohmic reflection layer 31 may cover 80% ormore, specifically 90% or more, of the upper surface of the mesa M.

The ohmic reflection layer 31 may include a reflective metal layer andthus can reflect light, which is generated in the active layer 25 andreaches the ohmic reflection layer 31, towards the substrate 21. Forexample, the ohmic reflection layer 31 may be composed of a singlereflective metal layer, without being limited thereto. In some exemplaryembodiments, the ohmic reflection layer 31 may include an ohmic layerand a reflective layer. The ohmic layer may be a metal layer, such as aNi layer, and the reflective layer may be a metal layer having highreflectivity, such as an Ag or Al layer. The ohmic reflection layer 31may further include barrier layers, for example, Ni, Ti, and Au layers.For example, the ohmic reflection layer may have a stack structure ofNi/Ag/Ni/Ti/Ni/Ti/Au/Ti.

The ohmic oxide layer 29 may cover the mesa M around the ohmicreflection layer 31. The ohmic oxide layer 29 may be formed of atransparent oxide layer, for example, indium tin oxide (ITO) or ZnO. Aside surface of the ohmic oxide layer 29 may be substantially flush withthe side surface of the mesa M. With the ohmic oxide layer 29 disposedaround the ohmic reflection layer 31, the light emitting diode can havean enlarged ohmic contact area, thereby reducing forward voltage of thelight emitting diode.

The lower insulation layer 33 covers the mesa M, the ohmic oxide layer29, and the ohmic reflection layer 31. The lower insulation layer 33 maycover the side surface of the mesa M along the periphery of the mesa M,and may also cover a portion of the first conductivity typesemiconductor layer 23 exposed along the periphery of the mesa M. Thelower insulation layer 33 covers the sidewall of the through-hole 30 ainside the through-hole 30 a and also covers the sidewall of theindented portion 30 b.

The lower insulation layer 33 has a first opening 33 a which exposes thefirst conductivity type semiconductor layer 23, and a second opening 33b which exposes the ohmic reflection layer 31. The first opening 33 amay be disposed in each of the through-hole 30 a and the indentedportion 30 b. In addition, the lower insulation layer 33 may expose thefirst conductivity type semiconductor layer 23 along the periphery ofthe mesa M.

The second opening 33 b of the lower insulation layer 33 exposes theohmic reflection layer 31. The lower insulation layer 33 may include aplurality of second openings 33 b, which may be disposed near one sideof the mesa M.

The lower insulation layer 33 may be composed of a single layer of SiO₂or Si₃N₄, without being limited thereto. Alternatively, the lowerinsulation layer 33 may have a multilayer structure including, forexample, a silicon nitride layer and a silicon oxide layer, or mayinclude a distributed Bragg reflector in which dielectric layers havingdifferent indexes of refraction such as a silicon oxide layer and atitanium oxide layer are alternately stacked one above another.

The first pad metal layer 35 a is disposed on the lower insulation layer33 and is insulated from the mesa M and the ohmic reflection layer 31 bythe lower insulation layer 33. The first pad metal layer 35 a contactsthe first conductivity type semiconductor layer 23 through the firstopenings 33 a of the lower insulation layer 33. The first pad metallayer 35 a may include an outer contact portion contacting the firstconductivity type semiconductor layer 23 around the mesa M and an innercontact portion contacting the first conductivity type semiconductorlayer 23 inside the through-hole 30 a. The outer contact portion of thefirst pad metal layer 35 a may be formed near the indented portion 30 bformed on the periphery of the mesa M and may also be formed near fourcorners of the mesa M. At least one of the inner and outer contactportions may be used and use of both the inner contact portion and theouter contact portion can enhance current spreading performance of thelight emitting diode.

The second pad metal layer 35 b is disposed on the lower insulationlayer 33 to be placed above the mesa M and is electrically connected tothe ohmic reflection layer 31 through the second openings 33 b of thelower insulation layer 33. The second pad metal layer 35 b may besurrounded by the first pad metal layer 35 a and a boundary region 35 abmay be formed therebetween. The lower insulation layer 33 is exposed tothe boundary region 35 ab, which is covered by the upper insulationlayer 37 described below.

The first pad metal layer 35 a and the second pad metal layer 35 b maybe formed of the same material by the same process. Each of the firstand second pad metal layers 35 a, 35 b may include an ohmic reflectionlayer, such as an Al layer, which may be formed on a bonding layer suchas a Ti, Cr or Ni layer. In addition, a protective layer composed of asingle layer or composite layer including Ni, Cr, Au and the like may beformed on the ohmic reflection layer. The first and second pad metallayers 35 a, 35 b may have a multilayer structure of, for example,Cr/Al/Ni/Ti/Ni/Ti/Au/Ti.

The upper insulation layer 37 covers the first and second pad metallayers 35 a, 35 b. In addition, the upper insulation layer 37 may coverthe first conductivity type semiconductor layer 23 along the peripheryof the mesa M. Here, the upper insulation layer 37 may expose the firstconductivity type semiconductor layer 23 along an edge of the substrate21.

The upper insulation layer 37 includes a first opening 37 a whichexposes the first pad metal layer 35 a and a second opening 37 b whichexposes the second pad metal layer 35 b. The first opening 37 a and thesecond opening 37 b may be disposed above the mesa M so as to face eachother. Particularly, the second opening 37 b may be disposed only in anupper region of the second pad metal layer 35 b.

Although the second opening 37 b is illustrated as completely exposingupper regions of the second openings 33 b of the lower insulation layer33 in this exemplary embodiment, the second opening 37 b of the upperinsulation layer may be spaced apart from the second openings 33 b ofthe lower insulation layer 33 in the lateral direction. That is, thesecond openings 33 b may be disposed outside the second opening 37 b anda plurality of second openings 37 b may be spaced apart from the secondopenings 33 b in the lateral direction.

The upper insulation layer 37 may be composed of a single layer of SiO₂or Si₃N₄, without being limited thereto. Alternatively, the upperinsulation layer 37 may have a multilayer structure including, forexample, a silicon nitride layer and a silicon oxide layer, or mayinclude a distributed Bragg reflector in which dielectric layers havingdifferent indexes of refraction such as a silicon oxide layer and atitanium oxide layer are alternately stacked one above another.

The first bump pad 39 a electrically contacts the first pad metal layer35 a exposed through the first opening 37 a of the upper insulationlayer 37, and the second bump pad 39 b electrically contacts the secondpad metal layer 35 b exposed through the second opening 37 b. As shownin FIG. 1 and FIG. 2, the first bump pad 39 a and the second bump pad 39b may be disposed only in the first opening 37 a and the second opening37 b, respectively, without being limited thereto. Alternatively, thefirst and second bump pads 39 a, 39 b may cover the first and secondopenings 37 a, 37 b to seal the first and second openings 37 a, 37 b,respectively.

The first bump pad 39 a is electrically connected to the firstconductivity type semiconductor layer 23 through the first pad metallayer 35 a, and the second bump pad 39 b is electrically connected tothe second conductivity type semiconductor layer 27 through the secondpad metal layer 35 b and the ohmic reflection layer 31. The second padmetal layer 35 b may be omitted and the second bump pad 39 b may bedirectly connected to the ohmic reflection layer 31.

As shown in FIG. 1, the second bump pad 39 b may be placed only in anupper region of the second pad metal layer 35 a, without being limitedthereto. Alternatively, the second bump pad 39 b may partially overlapthe first pad metal layer 35 a. In this exemplary embodiment, the upperinsulation layer 37 is disposed between the first pad metal layer 35 aand the second bump pad 39 b to insulate the first pad metal layer 35 afrom the second bump pad 39 b.

On the other hand, the side reflection layer 41 may be disposed on theside surfaces of the substrate 21. The side reflection layer 41 coversnot only the perpendicular side surface of the substrate 21 but also theinclined side surface thereof. The side reflection layer 41 may alsocover the side surface of the first conductivity type semiconductorlayer 23.

Although the side reflection layer 41 may be formed to cover all fourside surfaces of the substrate 21, other implementations are alsopossible. Alternatively, the side reflection layer 41 may be formed tocover one to three side surfaces of the substrate 21.

The side reflection layer 41 is spaced apart from the mesa M in thelateral direction. As shown in an enlarged circle of FIG. 2, the sidereflection layer 41 is spaced apart from the first pad metal layer 35 ain the lateral direction. Particularly, the side reflection layer 41 maybe disposed above the upper surface of the mesa M and thus is placedabove the exposed surface of the first conductivity type semiconductorlayer 23 around the mesa M. For example, a lower end of the sidereflection layer 41 may be flush with the exposed surface of the firstconductivity type semiconductor layer 23 and may be placed above theexposed surface of the first conductivity type semiconductor layer 23,as indicated by a dotted line. Accordingly, a portion of the exposedsurface of the first conductivity type semiconductor layer 23 around themesa M may be exposed to the outside between the side reflection layer41 and the upper insulation layer 37.

The side reflection layer 41 may include a metal reflection layer of Agor Al and a barrier layer such as Ni and/or Ti may be disposed on themetal reflection layer. Further, an anti-oxidation layer such as an Aulayer may be disposed on the barrier layer in order to prevent oxidationof the metal reflection layer. Furthermore, a bonding layer such as a Nilayer or a Ti layer may be interposed between the metal reflection layerand the substrate 21 in order to improve bonding characteristics of themetal reflection layer. The side reflection layer 41 may form ohmiccontact or Schottky contact with the substrate 21 and the firstconductivity type semiconductor layer 23.

The side reflection layer 41 may include a distributed Bragg reflectorinstead of the metal reflection layer or may further include anomnidirectional reflector (ODR) including a transparent oxide layerbetween the metal reflection layer and the substrate 21.

With the side reflection layer 41 disposed only on the side surfaces ofthe substrate 21 and the first conductivity type semiconductor layer 23,the side reflection layer 41 can be prevented from directly contacting(and short circuiting) the first pad metal layer 35 a, therebypreventing electrical interference by the side reflection layer 41.

When the side reflection layer 41 includes the metal reflection layeroverlapping the first pad metal layer 35 a, the side reflection layer 41can be directly electrically connected to the first pad metal layer 35 athrough various defects, such as pin holes or cracks in the upperinsulation layer 37. In this case, electrical characteristics of thelight emitting diode, such as forward voltage, can be significantlychanged depending upon the presence of contact between the sidereflection layer 41 and the first pad metal layer 35 a, thereby causingsignificant variation in electrical characteristics between lightemitting diodes. On the contrary, according to this exemplaryembodiment, the side reflection layer 41 is spaced apart from the firstpad metal layer 35 a, thereby enabling mass production of light emittingdiodes with less deviation in electrical characteristics.

FIG. 3 is a schematic cross-sectional view of a light emitting diode 200according to another exemplary embodiment of the present disclosure.

Referring to FIG. 3, the light emitting diode 200 according to thisexemplary embodiment is generally similar to the light emitting diode100 described with reference to FIG. 1 and FIG. 2 except that the upperinsulation layer 37 covers the inclined side surface of the substrate21.

That is, the upper insulation layer 37 covers the entirety of the firstconductivity type semiconductor layer 23 exposed around the mesa M, andalso covers the side surface of the first conductivity typesemiconductor layer 23 and the inclined side surface of the substrate21. Here, the upper insulation layer 37 does not cover the perpendicularside surface of the substrate 21.

On the other hand, the side reflection layer 41 covers the perpendicularside surface of the substrate 21 and also covers the upper insulationlayer 37 on the inclined side surface. In this structure, the lower endof the side reflection layer 41 may be flush with the exposed surface ofthe first conductivity type semiconductor layer 23 or may be disposedbelow the exposed surface of the first conductivity type semiconductorlayer 23, as indicated by a dotted line. Here, the lower end of the sidereflection layer 41 may be coplanar with or disposed above a horizontalplane of the upper insulation layer 37.

When the inclined side surface is formed by a scribing process, theinclined side surface can become a rough surface. In this case, the sidereflection layer 41 cannot be deposited on the inclined side surface ormay be easily removed therefrom even if the side reflection layer can bedeposited thereon. Thus, the upper insulation layer 37 is formed tocover the inclined side surface so as to allow stable formation of theside reflection layer 41.

FIG. 4 is a schematic cross-sectional view of a light emitting diode 300according to another exemplary embodiment of the present disclosure.

Referring to FIG. 4, the light emitting diode 300 according to thisexemplary embodiment is generally similar to the light emitting diode100 described with reference to FIG. 1 and FIG. 2 except that theinclined side surface of the light emitting diode 300 is placed closerto the upper surface of the substrate than the perpendicular sidesurface thereof. The inclined side surface of the substrate may beplaced adjacent the upper surface of the substrate 21, and theperpendicular side surface thereof may be placed adjacent the firstconductivity type semiconductor layer 23. The perpendicular side surfaceand the inclined side surface may be covered by the side reflectionlayer 41.

Since the inclined side surface is placed adjacent the upper surface ofthe substrate 21, the light emitting diode 300 according to thisexemplary embodiment may have a narrower viewing angle than the lightemitting diode 100 shown in FIG. 1 and FIG. 2.

FIG. 5 is a schematic cross-sectional view of a light emitting diode 400according to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 5, the light emitting diode 400 according to thisexemplary embodiment is generally similar to the light emitting diode300 described with reference to FIG. 4 except that the side reflectionlayer 41 does not cover the inclined side surface of the substrate. Thatis, the side reflection layer 41 covers the perpendicular side surfaceof the substrate 21 excluding the inclined side surface thereof

With this structure, the light emitting diode 400 may have a widerviewing angle than the light emitting diode 300 and the light emittingdiode 100.

As in this exemplary embodiment, the viewing angle of the light emittingdiode can be controlled by adjusting the location of the side reflectionlayer 41 on the light emitting diode.

FIG. 6 is a schematic cross-sectional view of a light emitting diode 500according to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 6, the light emitting diode 500 according to thisexemplary embodiment is generally similar to the light emitting diode400 described with reference to FIG. 5 except that the inclined sidesurface has a gentler inclination.

As shown in FIG. 5, the inclined side surface may be formed to have aninclination angle of about 10 to 20 degrees, particularly 10 to 15degrees, with respect to the perpendicular side surface. In thisexemplary embodiment, the inclined side surface may be formed to have aninclination angle of about 20 to 60 degrees, for example, 30 to 50degrees, with respect to the perpendicular side surface.

The inclination angle of the inclined side surface can be adjusted tocontrol the viewing angle of the light emitting diode while improvinglight extraction efficiency thereof.

FIG. 7 is a schematic cross-sectional view of a light emitting diode 600according to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 7, the light emitting diode 600 according to thisexemplary embodiment is generally similar to the light emitting diode100 described with reference to FIG. 1 and FIG. 2 except that thesubstrate 21 includes only the perpendicular side surface without theinclined side surface.

That is, the substrate 21 of the light emitting diode 600 according tothis exemplary embodiment includes the perpendicular side surface. Theside surface of the first conductivity type semiconductor layer 23 mayalso be flush with the perpendicular side surface of the substrate 21.

The side reflection layer 41 covers the perpendicular side surface ofthe substrate 21.

FIG. 8 is a schematic cross-sectional view of a light emitting diode 700according to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 8, the light emitting diode 700 according to thisexemplary embodiment is generally similar to the light emitting diode600 described with reference to FIG. 7 except that the side reflectionlayer 41 is formed in a plurality of band shapes covering the sidesurface of the substrate 21. The side surface of the substrate 21 isexposed through gaps between the bands of the side reflection layer 41.

The substrate 21 may have a rectangular shape, as shown in FIG. 1, andthe side reflection layer 21 may be formed in the band shape on eachside surface of the substrate 21. A band formed on one side surface ofthe substrate 21 may be connected to bands formed on other side surfacesthereof to form a loop formed along the side surfaces thereof.Alternatively, the bands may be discontinuously formed on the sidesurfaces of the substrate 21.

Light can be emitted through exposed regions of the side surfaces of thesubstrate 21, thereby increasing the viewing angle of the light emittingdiode 600 shown in FIG. 7.

FIG. 9A to FIG. 17D are schematic plan views and cross-sectional viewsillustrating a method of manufacturing a light emitting diode accordingto one exemplary embodiment of the present disclosure. FIGS. 9A, 10A,11A, 12A, 13A, 14A, 15A and 16A are plan views and FIGS. 9B, 10B, 11B,12B, 13B, 14B, 15B and 16B are cross-sectional views taken along lineA-A thereof.

Referring to FIG. 9A and FIG. 9B, a semiconductor stack 30 including afirst conductivity type semiconductor layer 23, an active layer 25 and asecond conductivity type semiconductor layer 27 are grown on a substrate21 and an ohmic oxide layer 29 is formed on the semiconductor stack 30.

The substrate 21 may be a sapphire substrate or a gallium nitride-basedsubstrate. The gallium nitride-based semiconductor layer may have ann-type dopant concentration of, for example, 7E17/cm³ to 9E17/cm³. Thefirst conductivity type semiconductor layer 23 may have an n-type dopantconcentration of, for example, 9E18/cm³ to 2E19/cm³.

The first conductivity type semiconductor layer 23, the active layer 25and the second conductivity type semiconductor layer 27 may be grown onthe substrate 21 within a chamber by any well-known method, such asmetal organic chemical vapor deposition (MOCVD) or molecular beamepitaxy (MBE).

The ohmic oxide layer 29 may be formed of, for example, ITO or ZnO. Theohmic oxide layer 29 may be formed by e-beam evaporation or sputteringand may cover the second conductivity type semiconductor layer 27 toform ohmic contact with the second conductivity type semiconductor layer27.

Referring to FIG. 10A and FIG. 10B, a mesa M is formed by patterning theohmic oxide layer 29 and the semiconductor stack 30. By forming the mesaM, the first conductivity type semiconductor layer 23 is exposed aroundthe mesa M. The mesa M has a through-hole 30 a and an indented portion30 b and may be formed to have partially cut corners. The ohmic oxidelayer 29 covers substantially the entire upper region of the mesa M andhas the same shape as the mesa M in plan view.

In this exemplary embodiment, the ohmic oxide layer 29 may be subjectedto patterning by wet etching using a photoresist pattern, and thesemiconductor stack 30 may be subjected to patterning by dry etching.However, it should be understood that other implementations are alsopossible and both the ohmic oxide layer 29 and the semiconductor stack30 may be subjected to patterning through dry etching. On the otherhand, patterning of the ohmic oxide layer 29 and the semiconductor stack30 may be performed using the same photoresist pattern.

Referring to FIG. 11A and FIG. 11B, the second conductivity typesemiconductor layer 27 is exposed by patterning the ohmic oxide layer 29and an ohmic reflection layer 31 is formed on an exposed region of thesecond conductivity type semiconductor layer 27. The ohmic reflectionlayer 31 includes a metal reflection layer, such as an Ag or Al layer,and may further include an ohmic metal layer, such as a Ni layer.Materials for the ohmic reflection layer 31 are described above withreference to FIG. 1 and FIG. 2 and detailed description thereof will beomitted for clarity. The ohmic reflection layer 31 may be formed bye-beam evaporation or sputtering.

Referring to FIG. 12A and FIG. 12B, a lower insulation layer 33 isformed to cover the ohmic oxide layer 29 and the ohmic reflection layer31. The lower insulation layer 33 also covers side surfaces of the mesaM and a sidewall of the through-hole 30 a. On the other hand, the lowerinsulation layer 33 has first openings 33 a which expose the firstconductivity type semiconductor layer 23 and second openings 33 b whichexpose the ohmic reflection layer 31.

For example, the first openings 33 a may be formed inside thethrough-hole 30 a and may also be formed near the indented portion 30 b.Furthermore, the lower insulation layer 33 may cover a portion of thefirst conductivity type semiconductor layer 23 along the periphery ofthe mesa M. With this structure, the first conductivity typesemiconductor layer 23 may be partially exposed along the periphery ofthe mesa M.

The second openings 33 b are placed on the ohmic reflection layer 31above the mesa M. A plurality of second openings 33 b may be arranged tobe biased to one side of the mesa M. The ohmic reflection layer 31 isexposed through the second openings 33 b. Although the lower insulationlayer 33 is shown as having five second openings 33 b in this exemplaryembodiment, it should be understood that other implementations are alsopossible. The lower insulation layer 33 may have one second opening 33 bor at least two second openings 33 b.

Referring to FIG. 13A and FIG. 13B, a first pad metal layer 35 a and asecond pad metal layer 35 b are formed on the lower insulation layer 33.The first pad metal layer 35 a is electrically connected to the firstconductivity type semiconductor layer 23 exposed through the firstopenings 33 a and the second pad metal layer 35 b is electricallyconnected to the ohmic reflection layer 31 exposed through the secondopenings 33 b.

The first pad metal layer 35 a may be connected to the firstconductivity type semiconductor layer 23 exposed through the firstopenings 30 a formed inside the through-hole 30 a and near the indentedportion 30 b, and may also be connected to the first conductivity typesemiconductor layer 23 near the corners of the mesa M. The first padmetal layer 35 a may include an inner contact portion contacting thefirst conductivity type semiconductor layer 23 through the through-hole30 a and outer contact portions contacting the first conductivity typesemiconductor layer 23 around the mesa M. The inner and outer contactportions of the first pad metal layer 35 a allow electric current to beuniformly spread over the entirety of the mesa M.

The second pad metal layer 35 b may be surrounded by the first pad metallayer 35 a and a boundary region 35 ab may be formed between the firstpad metal layer 35 a and the second pad metal layer 35 b. The second padmetal layer 35 b covers the second openings 33 b and may be placed onlyabove the mesa M.

The first pad metal layer 35 a and the second pad metal layer 35 b maybe formed of the same material by, for example, a lift-off process andthus may be placed on the same level.

Referring to FIG. 14A and FIG. 14B, an upper insulation layer 37 isformed on the first pad metal layer 35 a and the second pad metal layer35 b. The upper insulation layer 37 includes a first opening 37 a whichexposes the first pad metal layer 35 a and a second opening 37 b whichexposes the second pad metal layer 35 b. The upper insulation layer 37may cover the lower insulation layer 33 around the mesa M and may exposethe first conductivity type semiconductor layer 23 along the peripheryof the mesa M. The outer contact portions of the first pad metal layer35 a formed near the indented portion 30 b and the corners of the mesa Mare also covered by the upper insulation layer 37.

The second opening 37 b may be placed only in an upper region of thesecond pad metal layer 35 b. The first opening 37 a is placed only in anupper region of the first pad metal layer 35 a, particularly in an upperregion of the mesa M, without being limited thereto. The first opening37 a is spaced apart from the second opening 37 b.

Although each of the first opening 37 a and the second opening 37 b isillustrated as being formed singularly in this exemplary embodiment, theupper insulation layer 37 may have a plurality of first openings 37 aand a plurality of second openings 37 b.

Furthermore, although the second opening 37 b is illustrated asoverlapping the second openings 33 b of the lower insulation layer 33,the second opening 37 b may be formed to be spaced apart from the secondopenings 33 b in the horizontal direction so as not to overlap eachother.

Referring to FIG. 15A and FIG. 15B, a first bump pad 39 a and a secondbump pad 39 b are formed inside the first and second openings 37 a, 37 bof the upper insulation layer 37, respectively. The first and secondbump pads 39 a, 39 b may be formed of, for example, AuSn. The first andsecond bump pads 39 a, 39 b are pads bonded to a submount or a leadframe when the light emitting diode is mounted on the submount or thelead frame. The first and second bump pads 39 a, 39 b may be formed by awell-known process, such as a lift-off process.

In this exemplary embodiment, the first and second bump pads 39 a, 39 bare formed inside the first and second openings 37 a, 37 b,respectively, but are not limited thereto. Alternatively, the first andsecond bump pads 39 a, 39 b may be formed to completely cover the firstand second openings 37 a, 37 b, respectively.

Referring to FIG. 16A and FIG. 16B, after formation of the first andsecond bump pads 39 a, 39 b, a lower surface of the substrate 21 issubjected to grinding to reduce the thickness of the substrate 21 and aroughened surface R is formed on the ground lower surface of thesubstrate 21. The lower surface of the substrate 21 may be ground bylapping and/or polishing and the roughened surface R may be formed bydry and wet etching.

Referring to FIGS. 17A-17D, a method of forming a side reflection layer41 on a side surface of the substrate 21 will be described. FIGS.17A-17D show schematic cross-sectional views illustrating the method offorming the side reflection layer 41 of the light emitting diode 100according to the exemplary embodiment of the present disclosure.Although FIGS. 17A-17D show two light emitting diode regions formed bythe processes described with reference to FIG. 9 to FIG. 16B, a largernumber of light emitting diode regions may be formed on the substrate21, and the mesa M and the bump pads 39 a, 39 b may be formed on each ofthe light emitting diode regions.

Referring to FIG. 17A, after formation of the first and second bump pads39 a, 39 b, a scribing line LS is formed from the first conductivitytype semiconductor layer 21 into the substrate 21. The scribing line LScorresponds to an isolation region between light emitting diodes andthus, a plurality of scribing lines LSs may be formed in a mesh shape onthe substrate 21.

A photoresist layer 51 is coated onto the substrate 21 having theroughened surface R thereon. The photoresist layer 51 may be formed onthe substrate 21 by spin coating or the like.

Referring to FIG. 17B, individual light emitting diode regions aredivided from each other on a extendable tape, such as a blue tape, whichin turn is extended to separate the individual light emitting dioderegions from each other. Thereafter, the divided individual lightemitting diode regions are transferred to a support 61 such that theindividual light emitting diodes can be attached thereto. For example,the support 61 may be a polymer or polyimide film or another supportsubstrate. The divided individual light emitting diode regions may beindividually transferred to a polymer or polyimide film, or may beattached or transferred to the support substrate. Here, the mesa M maybe embedded in the support 61 such that the first conductivity typesemiconductor layer 23 exposed around the mesa M can adjoin an uppersurface of the support 61. However, it should be understood that otherimplementations are also possible. A contact region between the lightemitting diode regions and the support 61 may be adjusted and the firstconductivity type semiconductor layer 23 may be partially embedded inthe support 61 in the thickness direction.

On the other hand, the side surface of the substrate 21 in each of theindividual light emitting diode regions may have an inclined sidesurface formed by scribing and a perpendicular side surface formed bybreaking.

Referring to FIG. 17C, a side reflection layer 41 is deposited on eachof the individual light emitting diode regions. The side reflectionlayer 41 may be deposited thereon by, for example, sputtering. The sidereflection layer 41 includes a metal reflection layer such as an Aglayer or an Al layer. The side reflection layer 41 is the same as theside reflection layer described with reference to FIG. 1 and FIG. 2 anddetailed description thereof will be omitted.

The side reflection layer 41 is formed on the side surface of thesubstrate 21 to have a substantially uniform thickness on the inclinedside surface and the perpendicular side surface. Since the exposedsurface of the first conductivity type semiconductor layer 23 isshielded by the support 61, the side reflection layer 41 is preventedfrom being formed on the exposed surface of the first conductivity typesemiconductor layer 23. Therefore, the side reflection layer 41 can beprevented from overlapping the first pad metal layer 35 a.

Referring to FIG. 17D, the side reflection layer 41 can be removed fromthe upper side of the substrate 21 by removing the photoresist layer 51and the light emitting diode 100 is completed by removing the support 61therefrom.

On the other hand, although the scribing line LS is formed using a laserin this exemplary embodiment, the scribing line LS may be formed using ablade. In this case, the inclined side surface of the substrate 21 maybe formed to have a gentler inclination.

In addition, although the scribing line LS is formed after formation ofthe first and second bump pads 39 a, 39 b in this exemplary embodiment,the scribing line LS may also be formed before formation of the upperinsulation layer 37. In this case, the upper insulation layer 37 may beformed inside the scribing line LS, thereby providing a light emittingdiode 200 as shown in FIG. 3.

Viewing angles of a light emitting diode according to one exemplaryembodiment were measured in orthogonal directions. As a result, it couldbe seen that, when the side reflection layer 41 was not formed, thelight emitting diode had viewing angles of 130 and 150 degrees in theX-direction and the Y-direction, respectively, and when the sidereflection layer 41 was formed, the light emitting diode had viewingangles of 103.5 degrees and 115 degrees in the X-direction and theY-direction, respectively. Here, the substrate 21 had a thickness ofabout 250 μm. As such, when the side reflection layer 41 is employed, alight emitting diode having a viewing angle of 115 degrees or less canbe easily provided.

FIGS. 18A-18D show cross-sectional views illustrating a method ofmanufacturing a light emitting diode 300 according to a furtherexemplary embodiment of the present disclosure. As described withreference to FIG. 9A to FIG. 16B, light emitting diode regions areformed on a substrate 21, and a mesa M and bump pads 39 a, 39 b areformed on each of the light emitting diode regions.

Referring to FIG. 18A, after formation of the first and second bump pads39 a, 39 b, for example, a masking material 51 is coated onto thesubstrate 21 having a roughened surface R thereon. The masking material51 may be formed on the substrate 21 by spin coating or the like.

Then, a scribing line LS is formed on an upper surface of the substrate21, that is, from the masking material 51 side into the substrate 21.The scribing line LS corresponds to an isolation region between lightemitting diodes and thus a plurality of scribing lines LSs may be formedin a mesh shape on the substrate 21. The scribing line may be formedusing a laser and chemical treatment, such as phosphoric acid treatment,may be performed in order to remove debris from the side surface of thesubstrate 21 while relieving surface roughness of the substrate 21formed by the laser.

Referring to FIG. 18B, individual light emitting diode regions aredivided from each other on a stretchable tape such as a blue tape, whichin turn is stretched to separate the individual light emitting dioderegions from each other, as described with reference to FIG. 17B.Thereafter, the divided individual light emitting diode regions aretransferred to a support 61 such that the individual light emittingdiodes can be attached thereto.

On the other hand, the side surface of the substrate 21 in theindividual light emitting diode regions may have an inclined sidesurface formed by scribing and a perpendicular side surface formed bybreaking.

Referring to FIG. 18C, a side reflection layer 41 is deposited on eachof the individual light emitting diode regions. The side reflectionlayer 41 may be deposited thereon by, for example, sputtering. The sidereflection layer 41 includes a metal reflection layer such as an Aglayer or an Al layer. The side reflection layer 41 is the same as theside reflection layer described with reference to FIG. 1 and FIG. 2, anda detailed description thereof will be omitted.

The side reflection layer 41 is formed on the side surface of thesubstrate 21 to have a substantially uniform thickness on the inclinedside surface and the perpendicular side surface. Since the exposedsurface of the first conductivity type semiconductor layer 23 isshielded by the support 61, the side reflection layer 41 is preventedfrom being formed on the exposed surface of the first conductivity typesemiconductor layer 23. Therefore, the side reflection layer 41 can beprevented from overlapping the first pad metal layer 35 a.

Referring to FIG. 18D, the side reflection layer 41 can be removed fromthe upper side of the substrate 21 by removing the masking material 51and the light emitting diode 300 is completed by removing the support 61therefrom.

Although the scribing line LS is formed using a laser in this exemplaryembodiment, the scribing line LS may be formed using a blade. In thiscase, the inclined side surface of the substrate 21 may be formed tohave a gentler inclination.

FIG. 19 shows cross-sectional views illustrating a method ofmanufacturing a light emitting diode 400 according to yet anotherexemplary embodiment of the present disclosure.

The method of manufacturing the light emitting diode 400 according tothis exemplary embodiment is generally similar to the method ofmanufacturing the light emitting diode 300 described with reference toFIG. 18 except that the side reflection layer 41 does not cover theinclined side surface of the substrate 21.

In this exemplary embodiment, after formation of the scribing line usinga laser, surface roughness of the substrate 21 formed by laser scribingis adjusted by adjusting chemical treatment, such as phosphoric acidtreatment. A rough surface may be formed on the inclined side surface bylaser scribing and the side reflection layer 41 may be formed on theside surface of the substrate excluding the rough surface by reducing atime for phosphoric acid treatment.

Accordingly, the height of the side reflection layer 41 can be reducedwith increasing depth of laser scribing, thereby increasing the viewingangle of the light emitting diode.

FIGS. 20A-20D show cross-sectional views illustrating a method ofmanufacturing a light emitting diode 500 according to yet anotherexemplary embodiment of the present disclosure.

As described with reference to FIG. 9A to FIG. 16B, light emitting dioderegions are formed on a substrate 21, and a mesa M and bump pads 39 a,39 b are formed on each of the light emitting diode regions.

Referring to FIG. 20A, after formation of the first and second bump pads39 a, 39 b, a scribing line BS is formed using a blade on an uppersurface of the substrate 21 having a roughened surface R thereon. Thescribing line BS corresponds to an isolation region between lightemitting diodes and thus a plurality of scribing lines BSs may be formedin a mesh shape on the substrate 21.

Then, for example, a masking material 51 is coated onto the substrate21. The masking material 51 may be formed on the substrate 21 by spincoating or the like. The scribing line BS formed using a blade is formedof relatively wide V-shaped grooves. Thus, the scribing line is filledwith the masking material 51.

Referring to FIG. 20B, individual light emitting diode regions aredivided from each other on a stretchable tape such as a blue tape, whichin turn is stretched to separate the individual light emitting dioderegions from each other, as described with reference to FIG. 17B.Thereafter, the divided individual light emitting diode regions aretransferred to a support 61 such that the individual light emittingdiodes can be attached thereto.

The side surface of the substrate 21 in the individual light emittingdiode regions may have an inclined side surface formed by a blade and aperpendicular side surface formed by breaking.

Referring to FIG. 20C, a side reflection layer 41 is deposited on eachof the individual light emitting diode regions. The side reflectionlayer 41 may be deposited thereon by, for example, sputtering. The sidereflection layer 41 includes a metal reflection layer such as an Aglayer or an Al layer. The side reflection layer 41 is the same as theside reflection layer described with reference to FIG. 1 and FIG. 2 anddetailed description thereof will be omitted.

The side reflection layer 41 is formed on the perpendicular side surfaceto have a substantially uniform thickness. However, since the inclinedside surface is covered by the masking material 51, the side reflectionlayer 41 is prevented from being formed on the inclined side surface. Inaddition, since the exposed surface of the first conductivity typesemiconductor layer 23 is shielded by the support 61, the sidereflection layer 41 is prevented from being formed on the exposedsurface of the first conductivity type semiconductor layer 23.Therefore, the side reflection layer 41 can be prevented fromoverlapping the first pad metal layer 35 a.

Referring to FIG. 20D, the side reflection layer 41 can be removed fromthe upper side of the substrate 21 by removing the masking material 51and the light emitting diode 500 is completed by removing the support 61therefrom.

Although the scribing line LS is formed using a laser in this exemplaryembodiment, the scribing line LS may be formed using a blade. In thiscase, the inclined side surface of the substrate 21 may be formed tohave a gentler inclination.

In the above description, various techniques for forming the sidereflection layer 41 using laser scribing or blade scribing have beendescribed.

The substrate 21 may be divided using a stealth laser that forms a focusinside the substrate 21. In this case, the side surface of the substrate21 is formed to have a perpendicular side surface. Accordingly, thelight emitting diode 600 of FIG. 7 can be manufactured by a dicingtechnique using the stealth laser. In addition, a rough surface may beformed in a band shape along the side surface of the substrate 21through irradiation using the stealth laser, and the light emittingdiode 700 of FIG. 8 can be manufactured based on the fact that the sidereflection layer 41 is not compatible with the rough surface.

FIG. 21 is a schematic cross-sectional view of a light emitting moduleaccording to one exemplary embodiment of the present disclosure.

Referring to FIG. 21, the light emitting module includes a supportsubstrate 71, a light emitting diode 100, and a wavelength converter 81.The light emitting module may further include a white barrier layer 75.

The light emitting diode 100 is the same as the light emitting diodedescribed with reference to FIG. 1 and FIG. 2, and is flip bonded onto asupport substrate 71, on which the first and second pads 73 a, 73 b aredisposed, via the first and second bump pads 39 a, 39 b. The supportsubstrate 71 may be, for example, a submount, a printed circuit board,or a lead frame.

On the other hand, a white barrier layer 75 may cover the side surfaceof the light emitting diode 100. The white barrier layer 75 may beformed by mixing, for example, TiO2 with a silicone resin or an epoxyresin. The white barrier layer 75 can have defects, such as crackstherein, over time. Thus, when the white barrier layer 75 is directlyformed on the side surface of the light emitting diode without the sidereflection layer 41, light emitted from the light emitting diode canleak through the white barrier layer 75. However, according to theexemplary embodiments, the side reflection layer 41 is formed on theside surface of the light emitting diode, thereby providing a lightemitting module that does not suffer from light leakage even after usefor a long period of time.

The wavelength converter 81 such as a phosphor sheet or a wavelengthconverting plate may be disposed on an upper side of the light emittingdiode 100. The wavelength converting plate 81 may contain ceramic platephosphors, particularly, phosphor-in-glass (PIG) or SiC phosphors. Withthis structure, it is possible to provide a wavelength converter thatcan be used for a long time by preventing discoloration under hightemperature conditions.

The wavelength converting plate 81 may be attached to the light emittingdiode 100 using a bonding agent, or may be attached to the white barrierlayer 75 or other components. Thus, the wavelength converting plate 81may be disposed above the light emitting diode 100 to be spaced apartfrom the light emitting diode 100.

Although this exemplary embodiment is illustrated using the lightemitting diode 100 by way of example, other light emitting diodes 200,300, 400, 500, 600 or 700 may also be used.

The light emitting module according to this exemplary embodiment may beapplied to automobile headlamps, camera flashes, or lighting.

FIG. 22 is a schematic cross-sectional view of a light source moduleaccording to one exemplary embodiment of the present disclosure.

Referring to FIG. 22, the light source module includes a supportsubstrate 71, a light emitting diode 100, a wavelength converter 81, anda lens 91. The light emitting diode 100 is the same as the lightemitting diode described with reference to FIG. 1 and FIG. 2, and isflip bonded to a support substrate 71, on which the first and secondpads 73 a, 73 b are disposed, via the first and second bump pads 39 a,39 b. The support substrate 71 may be, for example, a printed circuitboard.

The lens 91 is disposed above the light emitting diode 100. The lens 91has a lower surface and an upper surface, in which the lower surfaceincludes a concave portion receiving light emitted from the lightemitting diode 100 and the upper surface has a light exit surfacethrough which light exits the lens. The concave portion of the lowersurface may be surrounded by a flat surface.

In addition, the upper surface of the lens 91 may include a concaveportion placed at the center thereof and a convex portion placed aroundthe concave portion. The convex portion may be formed to surround theconcave portion.

The lens 91 is a light dispersing lens configured to spread light.However, it should be understood that other implementations are alsopossible. That is, the lens 91 having various shapes may be coupled tothe light emitting diode 100 to realize various light patterns.

Although the light emitting diode 100 is flip bonded to the supportsubstrate 71 in the light source module according to this exemplaryembodiment, other light emitting diodes 200, 300, 400, 500, 600 or 700may also be mounted on a support substrate 91.

The light source module according to this exemplary embodiment may besuitably applied to, for example, a large TV or a camera flash.

FIG. 23 is a schematic perspective view of an automobile 1000 includingheadlamps 1100 to which light emitting diodes according to exemplaryembodiments of the present disclosure are applied.

Referring to FIG. 23, the light emitting diode 100, 200, 300, 400, 500,600 or 700 according to the exemplary embodiments of the presentdisclosure is provided to headlamps 1100 mounted on a front side of anautomobile 1000. In this exemplary embodiment, the headlamps 1100include fog lamps and headlamps for securing a forward view of a driverin day or at night.

The headlamps 1100 may be mounted on both front sides of the automobile1000 and may have various shapes according to driver preference. Inaddition, the headlamps 1100 mounted on both front sides of theautomobile 1000 may have a symmetrical structure with respect to eachother or may have different structures.

The light emitting diode may be provided to the headlamps 1100 in theform of the light source module as described with reference to FIG. 21.However, it should be understood that other implementations are alsopossible and the light emitting diode may be provided in the form ofvarious shapes of light emitting modules.

FIG. 24 is a schematic perspective view of a mobile device 2000including a camera flash 2300 to which a light emitting diode accordingto exemplary embodiments of the present disclosure is applied.

Referring to FIG. 24, the mobile device 2000 includes a camera module2100 and a flash module 2300. The light emitting diode 100, 200, 300,400, 500, 600 or 700 according to the exemplary embodiments of thepresent disclosure is provided to the flash module 2300. The flashmodule 2300 supplies light to an object when the camera module 2100 isoperated to photograph the object.

The light emitting diode may be provided to the camera module 2100 inthe form of the light source module as described with reference to FIG.21. However, it should be understood that other implementations are alsopossible and the light emitting diode may be provided in the form ofvarious shapes of light emitting modules.

Although certain exemplary embodiments have been described herein, itshould be understood by those skilled in the art that these embodimentsare given by way of illustration only, and that various modifications,variations, and alterations can be made without departing from thespirit and scope of the invention. Therefore, the scope of the inventionshould be limited only by the accompanying claims and equivalentsthereof.

What is claimed is:
 1. A light emitting diode comprising: asemiconductor stack comprising a first conductivity type semiconductorlayer having a first surface and a second surface opposing the firstsurface; a second conductivity type semiconductor layer and an activelayer interposed between the first conductivity type semiconductor layerand the second conductivity type semiconductor layer; a mesa disposed onthe first surface of the first conductivity type semiconductor layer andcomprising the first conductivity type semiconductor layer, the activelayer, and the second conductivity type semiconductor layer; an ohmiclayer electrically connected to the second conductivity typesemiconductor layer; a side reflection layer covering outermost sidesurfaces of at least the first conductivity type semiconductor layer;and a first bump pad and a second bump pad disposed under the ohmiclayer and electrically is connected to the first conductivity typesemiconductor layer and the second conductivity type semiconductorlayer, respectively, wherein the outermost side surfaces of the firstconductivity type semiconductor layer are chemically treated after beingphysically isolated.